In a semiconductor device lithography process, an original pattern formed on a mask is transferred to a wafer serving as a substrate of the semiconductor device. Drawing of the original pattern onto the mask is performed, for example, using an electron beam lithography apparatus.
In recent years, in order to improve a throughput, a multi-beam type electron beam lithography apparatus capable of drawing a pattern using a plurality of electron beams has come into use. In such a type of the electron beam lithography apparatus, an electron beam emitted from a single electron source is divided into multiple beams (multiplexed) as the electron beam passes through an aperture having a plurality of holes. The ON/OFF control of multiple electron beams are independently performed, for example, by a blanking aperture array (BAA).
Since the BAA is disposed in a vacuum lens barrel provided with an electron gun or the like for emitting an electron beam, its size is restricted. For this reason, a data format processed by the BAA is selected such that a control circuit of the BAA becomes as simple as possible. Meanwhile, image data of the pattern drawn by the electron beam lithography apparatus is designed, for example, using a computer-aided design (CAD) tool and is output in a bitmap format.
In order to perform the ON/OFF control of the electron beam using the BAA, it is necessary to convert the image data representing the pattern to be drawn into a format suitable for an interface of the BAA.
If an error occurs in conversion of the image data described above, a product yield is degraded. Thus, various techniques for avoiding such a patterning error have been proposed.
In the prior art, an error of the drawing data is detected by comparing a checksum of the data obtained before being supplied to the BAA and a checksum of the data supplied to the BAA. In the technique of JP H08-297586 A, a damage of the drawing data is detected by calculating and comparing an expected parity bit of the data obtained after sorting. In the technique of JP H09-74060 A (corresponding to U.S. Pat. No. 5,866,300), however, it is difficult to detect a conversion error while the damaged data can be detected. In the technique of JP H08-297586 A, for example, if a conversion error occurs due to a change of the data arrangement sequence, a parity check may be successful erroneously. Thus, it is difficult to detect abnormality. For this reason, if a conversion error described above occurs, a long time is necessary to perform troubleshooting. As a result, a system downtime may be prolonged.